Warped ideas about the scary ways people can contract a sexually transmitted infection abound. There’s the notion that you can get an STI from a toilet seat, the myth that an STI is always a sign of an unfaithful partner, and the nerve-wracking fear that STIs can emerge “randomly.” The worst part about these myths isn’t that they’re false — it’s that they obscure the real problems about STI transmission.

Let’s get one thing clear: It’s safe to say that getting an STI “randomly” isn’t possible, says Dr. Peter Leone, a professor of medicine at the University of North Carolina, Chapel Hill, who specializes in STIs. He means that a person can’t get an STI without engaging in an activity known to spread disease.

“There’s nothing random about getting a sexually transmitted infection,” Leone tells Inverse. “People get them. I think one of the big misconceptions is that they’re uncommon.”

Cases of chlamydia in women aged 15 to 24 in 2017. STIs usually spread in networks.

How Do STIs Actually Spread?

There’s been a recent resurgence of notorious STIs: In the United States, the incidence of primary and secondary syphilis infections rose by 76 percent since 2013, and chlamydia infections rose by 45 percent over the same timeframe, reports the CDC.

Infections like this aren’t random, asserts Leone. By and large they are spread through sexual activity. He’s more concerned with why these infections remain so common despite widespread public health efforts to control them.

“There are several things that go into risk.”

Part of the answer is that STIs get transmitted in different ways, so there’s no single solution that will prevent them all at once. Gonorrhea, chlamydia, and HIV all require the exchange of the bodily fluids mentioned above. Others, like HPV (for which there is a highly effective vaccine), can be spread through skin-to-skin contact. Trichomoniasis, an STI caused by a parasite, is a special case: While it is most often spread through sexual contact, it can also be passed on through sharing damp personal items like towels, wet clothing, or toilet seats.

But outside of those factors, the continuing spread of STIs can be chalked up to the complicated social and societal factors that put certain people at risk.

“There are several things that go into risk,” Leone says. “One of them has to do with the type of sex you engage in. The other has to do with your selection of partners and that sexual network that they’re in.”

Who Is at Risk?

Because it takes more than one person to spread an STI, these diseases move in networks. These networks can be thought of as geographical: For instance, the CDC reports that 52 percent of the new HIV cases in 2017 occurred in Southern states.

But the networks can also be population-based. The rates of STI incidence in black and Hispanic communities, for example, are far higher than they are for white Americans, note the CDC and other scientists. This disparity largely comes down to a lack of access to STI screening, care, and education.

Racial disparities in STI care were implicated directly in May 2018, when reports of record STI cases in California caused alarm over what some doctors called a “decimation” of public health infrastructure. Leone says that this is a recurring problem.

Rates of chlamydia tend to be higher for racial and ethnic minorities in the United States.

“So for minorities there are much higher risks with sexually transmitted infections that have to do with marginalization of populations, institutional racism in terms of access to care,” he says.

Robert Kirkcaldy, a medical officer in CDC’s Division of STD Prevention, adds that the idea of sexual networks is a growing area of research that the field is pursuing. “Some of these research areas include investigating how quickly different STDs spread among large groups of people and how different kinds of connections between groups of partners (often called “networks”) speed up or slow down STD transmission,” he tells Inverse.

How Can You Avoid Getting STIs?

Aside from finding ways to reverse the thoroughly depressing trends regarding equitable access to healthcare and STI care, there are some obvious things you can do as an individual to avoid contracting STIs. Most important is to use a condom and/or dental dam during sexual activity, which acts as a physical barrier to the bodily fluids transmitted during sex. Getting tested according to CDC guidelines, reducing your number of sexual partners, and being in a mutually monogamous relationship all tend to reduce risk overall.

But research on sexual networks has suggested that controlling for partner choice can also eliminate some risks, Leone and Kirkcaldy add. Speaking statistically, says Leone, the chance of getting an STI in the first place increases with the amount of sexual partners someone has had, which is sometimes a factor of age.

“For younger adults, meaning teens and people in their twenties, we tell them to ‘eat at home’ — meaning your risk is probably less having sex with someone who is around your age as opposed to someone who is older,” he says.

Kirkcaldy and Leone are adamant that there’s no such thing as a random STI infection. What these infections are instead are products of behavior or, sadly, inequalities in the healthcare system that allow them to persist.

There are only unexpected infections — which are due to lack of education, not some sudden emergence of STI-causing bacteria. The best way to prevent them from occurring unexpectedly is to read up on the ways that STIs are spread and not spread — and to act accordingly.